1. Field of the Invention
This invention relates to a composite closure for a container for the packaging of a product under at least partial vacuum. The composite closure includes a metal lid that has a portion whose position is altered by a loss of vacuum within the container to give a visual indication of such loss of vacuum, and a plastic ring to secure the metal lid to the rim of the container. The plastic ring has a tamper indicating band at its lowermost marginal edge, and this tamper indicating band must be irreparably and visibly damaged upon the first removal or attempted removal of the closure from the container to provide a visible indication of any prior attempt to open the container.
2. Description of the Prior Art
Many food products which are packaged in glass jars are packaged under a partial vacuum to prevent spoilage or to preserve flavor, and it is important that the closure for such a container be able to seal the container properly to maintain the vacuum in the container until the first opening thereof. It has also been recognized that it is desirable for a closure for a container for a vacuum-packed product to incorporate means which will indicate the presence or absence of the desired degree of vacuum, to ensure the freshness and wholesomeness of the packaged product when the package is purchased and when it is opened, and the prior art is familiar with metal closures which incorporate such a feature. For example, U.S. Pat. No. 3,152,711 (G. V. Mumford et al.), which is assigned to the assignee of this application, discloses a one-piece metallic closure in which the top panel of the closure incorporates a domed central portion, which domed central portion is deflected downwardly by the presence of a suitable degree of partial vacuum in the associated container. Because of the inherent elasticity of the metal of the closure, the deflected domed central portion will return to its normal position upon the release of the vacuum and the resulting repressurization of the container, thereby providing an indication of such release of container vacuum which is detectable visually or by various types of electro-mechanical or electro-optical inspection equipment. U.S. Pat. Nos. 3,062,396 (G. J. Foss et al.), 3,160,302 (G. F. Chaplin), and 4,533,059 (W. J. Kapolas et al.) also disclose one-piece metallic vacuum indicating closures that operate in a similar manner, and U.S. Pat. No. 3,836,033 (A. Podesta) discloses a two-piece vacuum indicating closure having a metallic closure panel and a separate metallic closure panel retention skirt that otherwise also operates in a similar manner.
U.S. Pat. Nos. 4,093,094 (N. J. Smalley et al.) and 4,121,729 (C. W. Husum), which are assigned to the assignee of this application, disclose two piece vacuum indicating closures that are useful in a home canning system. According to the teachings of these references, certain advantages are obtained in a vacuum indicating closure when at least the skirt portion thereof is formed from a thermoplastic material. However, the closure systems of the aforesaid U.S. Pat. Nos. 4,093,094 and 4,121,729 require separate handling of the metal lid and plastic ring components thereof, since the closure systems of such references do not incorporate means to positively interlock the metal lid and the plastic ring, and, thus, the closure systems of the aforesaid U.S. Pat. Nos. 4,093,094 and 4,121,729 are not suitable for use in a packaging plant where it is necessary to mechanically apply closures to containers at a high rate of speed in order to be able to meet the cost constraints that apply to any such industrial operation. Further, while U.S. Pat. No. 4,694,970 (T. H. Hayes) shows a composite closure with a metal lid and a plastic lid engaging ring in which the ring is provided with a disengageable tamper indicating band, this closure is not disclosed as having vacuum indicating characteristics, and the vacuum indicating closures of the various prior art patents heretofore identified do not incorporate separate tamper-indicating design features. These closures rely upon the change in the position of the domed central portion of the closure metal lid, which occurs upon the loss of vacuum in the associated container, to provide evidence of the prior opening of the container. However, the position of the domed central portion of the metal lid of a vacuum indicating closure is easily reversible and its position is not as visually detectable as is the irreparable damage that is sustained by many molded plastic closures of the tamper-indicating type, and, in any event, the domed central portion of the metal lid of the closure will change its position upon a mere loss of vacuum in the associated container resulting from a sealing irregularly between the closure and the container, and does not, necessarily, indicate that the package in question has experienced a tampering attempt. U.S. Pat. No. 3,460,701 (J. C. Powalowski et al.) does disclose a two-piece, tamper-evident closure that includes a metal lid and a plastic ring to maintain such metal lid in contact with the associated container, but the two-piece closure of this reference is of the snap-on type, and, thus, requires the use of a cumbersome lifting ring in the top of the closure retaining ring to remove the two-piece closure from the container, the deformation of the lifting ring during the removal of the closure resulting in the tamper-indicating characteristics of the product.